Method for fabricating a liquid crystal display device having cholesteric liquid crystal color filter layer with high aperture ration

ABSTRACT

A fabricating method of a substrate for a liquid crystal display device includes: coating a cholesteric liquid crystal material on a substrate to form a cholesteric liquid crystal layer, the substrate having a plurality of sub-pixel regions; disposing a mask having a plurality of open portions over the cholesteric liquid crystal layer; irradiating the cholesteric liquid crystal layer through the mask and curing the cholesteric liquid crystal layer, wherein each open portion is smaller than each sub-pixel region.

This application is a Divisional of prior application Ser. No.10/667,360, filed Sep. 23, 2003.

This application claims the benefit of Korean Patent Application No.2002-81963, filed on Dec. 20, 2002, which is hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to liquid crystal display devices, andmore particularly to liquid crystal display devices using a cholestericliquid crystal color filter layer.

2. Discussion of the Related Art

Liquid crystal display (LCD) devices are developed as next generationdisplay devices because of their characteristics of light weight, thinprofile, and low power consumption.

Among the various types of LCD devices commonly used, active matrix LCD(AM-LCD) devices, in which thin film transistors (TFTs) and pixelelectrodes connected to the TFTs are disposed in matrix, have beendeveloped because of their high resolution and superior display ofmoving images.

FIG. 1 is a schematic plan view of a liquid crystal display deviceaccording to the related art.

In FIG. 1, a plurality of gate lines 14 are formed along a firstdirection and a plurality of data lines 24 are formed along a seconddirection perpendicular to the first direction. The gate line 14 crossesthe data line 24 to define a sub-pixel region “Psub.” A thin filmtransistor (TFT) “T” is formed near a cross of the gate line 14 and thedata line 24. A pixel electrode 30 is connected to the TFT “T.” A blackmatrix 52 (hatched area) is formed at borderline between the sub-pixelregions “Psub.” The black matrix 52 has an open portion 51 exposing thepixel electrode 30. Even though not shown in FIG. 1, a color filterlayer including red, green and blue sub-color filters is formed in theopen portion 51. Each of the sub-color filters corresponds to thesub-pixel region “Psub.” The color filter layer displaying colors byfiltering light is generally formed of a photosensitive resin through apigment dispersion method.

FIG. 2 is a schematic cross-sectional view, which is taken along a line“II—II” of FIG. 1, illustrating a liquid crystal display deviceaccording to the related art.

In FIG. 2, first and second substrates 10 and 50 face and are spacedapart from each other. A plurality of sub-pixel regions “Psub” aredefined in the first and second substrates 10 and 50. A gate insulatinglayer 16 is formed on an inner surface of the first substrate 10, and adata line 24 is formed on the gate insulating layer 16 at a borderbetween the sub-pixel regions “Psub.” A passivation layer 28 is formedon the data line 24, and a pixel electrode 30 is formed on thepassivation layer 28 in the sub-pixel region “Psub.”

A black matrix 52 is formed on an inner surface of the second substrate50 to correspond to the data line 24. A color filter layer 54 includingred, green and blue sub-color filters 54 a, 54 b and 54 c is on theblack matrix 52 and the inner surface of the second substrate 50. Eachof the red, green and blue sub-color filters 54 a, 54 b and 54 ccorresponds to the sub-pixel region “Psub.” A common electrode 58 isformed on the color filter layer 54. A liquid crystal layer 70 is formedbetween the pixel electrode 30 and the common electrode 58.

Even though not shown in FIG. 2, the red, green and blue sub-colorfilters 54 a, 54 b and 54 c are sequentially formed through a pigmentdispersion method including: a step of coating a photosensitive resin onthe black matrix 52; a step of aligning a mask having an open portioncorresponding to the sub-pixel region “Psub”; a step of exposing thecoated photosensitive resin through the mask; a step of developing theexposed photosensitive resin; and a step of curing the developedphotosensitive resin. The absorption-type color filter layer 54 filterslight to transmit only light having a wavelength band corresponding to aspecific color. Accordingly, as the color filter layer 54 is used over along time period, color characteristics and transmittance are reduced.

To solve these problems, a color filter layer using cholesteric liquidcrystal (CLC) which selectively reflects and transmits light has beendeveloped. Because the CLC itself selectively reflects and transmitslight, high color purity can be obtained. Moreover, an additionalreflecting layer can be omitted when the CLC used for a reflective typeLCD device. In the CLC, liquid crystal molecules are aligned to have ahelical structure. The helical structure has a direction of circulationand a helical pitch. The helical pitch is a distance from a liquidcrystal molecule layer having a specific alignment state to a nextliquid crystal molecule layer having the same alignment state, and acolor reflected by the CLC is determined by the helical pitch. A centralwavelength of reflected light is a function of the helical pitch “p” andthe average refractive index “n_(avg)” of the CLC. (λ=n_(avg)·p). Forexample, when a CLC has an average refractive index of about 1.5 and ahelical pitch of about 430 nm, a central wavelength of reflected lightis about 650 nm and the CLC reflects red colored light. Similarly, theCLC can be formed to have corresponding helical pitch, therebyreflecting green or blue colored light.

FIG. 3 is a schematic cross-sectional view, taken along a line “II—II”of FIG. 1, illustrating a liquid crystal display device using acholesteric liquid crystal color filter layer according to the relatedart.

In FIG. 3, first and second substrates 110 and 150 having a plurality ofsub-pixel regions “Psub” face each other and are spaced apart from eachother. A light absorption layer 112 is formed on an inner surface of thefirst substrate 110, and a cholesteric liquid crystal color filter (CCF)layer 114 is formed on the light absorption layer 112. The CCF layer 114includes red, green and blue CCFs 114 a, 114 b and 114 c in eachsub-pixel region “Psub.” A common electrode 116 is formed on the CCFlayer 114. A gate insulating layer 152 is formed on an inner surface ofthe second substrate 150 and a data line 154 is formed on the gateinsulating layer 152 corresponding to a border between the sub-pixelregions “Psub.” A black matrix 156 is formed on the data line 154 and apassivation layer 158 is formed on the black matrix 156. A pixelelectrode 160 is formed on the passivation layer 158 in each sub-pixelregion “Psub.” A liquid crystal layer 170 is formed between the commonelectrode 116 and the pixel electrode 160.

A retardation layer 162 and a polarizing layer 164 are sequentiallyformed on an outer surface of the second substrate 150 to prevent phasedelay of light and improve optical efficiency. For example, theretardation layer 162 can be a quarter wave plate (QWP), which delaysphase by λ/4, and the polarizing layer 164 can be a linear polarizer,which transmits only light having a polarization axis parallel to thetransmission axis of the polarizing layer 164.

When incident light enters a reflective LCD device using the CCF layer114, only light corresponding to a specific wavelength band selectivelyreflects from the CCF layer 114. Other light passes through the CCFlayer 114 and then is absorbed into the light absorption layer 112. Whenthe reflected light again passes through the second substrate 150, theblack matrix 156 shields light passing through the liquid crystal layer170 in a portion not driven by the pixel electrode 160. Contrary to anLCD device using an absorption type color filter layer, a reflective LCDdevice using a CCF layer uses selective reflection property of the CCFlayer. Accordingly, the CCF layer is formed on the first substrate, andthe black matrix is formed on the second substrate to shield leakagelight and prevents light entrance into a thin film transistor (TFT). Asa result, the CCF layer and the black matrix are formed on differentsubstrates, respectively.

In general, photochromic CLC, whose helical pitch is determinedaccording to irradiation energy of ultra violet (UV) light, is used forthe CCF layer 114. The CCF layer 114 is formed through a coloring methodwhere UV light having different energies is irradiated onto aphotochromic CLC layer in each of red, green and blue sub-pixel region“Psub” and then the irradiated CLC layer is cured. When the CCF layer114 is formed through the coloring method, the helical pitchcontinuously varies in border portions between red, green and bluesub-pixel regions “Psub.” Thus, each sub-pixel region “Psub” does notdisplay its own color distinctively. Instead, there exist color-blurringregions “A” in the border portions between sub-pixel regions “Psub.” Forexample, the CCF layer 114 in the color-blurring region “A” between thered and green sub-pixel regions “Psub” reflects yellow colored light.Similarly, the CCF layer 114 in the color-blurring region between thegreen and blue sub-pixel regions “Psub” reflects cyan colored light, andthe CCF layer 114 in the color-blurring region between the blue and redsub-pixel regions “Psub” reflects magenta colored light.

FIG. 4A is a schematic cross-sectional view of a substrate having anabsorption type color filter layer according to the related art.

In FIG. 4A, a black matrix 132 is formed on a substrate 130 and a colorfilter layer 134 is formed on the black matrix 132. The color filterlayer 134 includes red, green and blue color filters 134 a, 134 b and134 c in each sub-pixel region “Psub.” Even though not shown in FIG. 4A,the red, green and blue color filters 134 a, 134 b and 134 c are formedthrough coating, exposing, developing and curing processes of respectivephotosensitive resin. Accordingly, a color blurring between adjacentcolor filters can be prevented. In addition, even when a color blurringoccurs, the black matrix 132 can shield the color blurring due toresolution of an exposure apparatus for the color filter layer. Forexample, when a width of each sub-pixel region “Psub,” i.e., each of thered, green and blue color filters 134 a, 134 b and 134 c, is about 93μm, a width of the black matrix 132 is about 24 μm.

FIG. 4B is a schematic cross-sectional view of a substrate having acholesteric liquid crystal color filter layer fabricated through acoloring method excluding a blue coloring process according to therelated art.

In FIG. 4B, a light absorption layer 142 is formed on a substrate 140and a cholesteric liquid crystal color filter (CCF) layer 144 is formedon the light absorption layer 142. The CCF layer 144 includes red, greenand blue CCFs 144 a, 144 b and 144 c in each sub-pixel region “Psub.”The red and green CCFs 144 a and 144 b are formed through coating andcoloring processes of blue colored cholesteric liquid crystal (CLC),while the blue CCF 144 c is formed through coating process of bluecolored CLC. When a coloring process for a sub-pixel region “Psub” isperformed, a color blurring is generated at a peripheral portion of eachCCF 144 a and 144 b. Since a blue coloring process is not performed, acolor blurring does not occur at a peripheral portion of the blue CCF144 c. Accordingly, a first color blurring region “A1” between the blueand red CCFs 144 c and 144 a or between the blue and green CCFs 144 cand 144 b has a smaller area than a second color blurring region “A2”between the red and green CCFs 144 a and 144 b.

FIG. 4C is a schematic cross-sectional view of a substrate having acholesteric liquid color filter layer fabricated through a coloringmethod including a blue coloring process according to the related art.

In FIG. 4C, a light absorption layer 182 is formed on a substrate 180and a cholesteric liquid crystal color filter (CCF) layer 184 is formedon the light absorption layer 182. The CCF layer 184 includes red, greenand blue CCFs 184 a, 184 b and 184 c in each sub-pixel region “Psub.”The red, green and blue CCFs 184 a, 184 b and 184 c are formed throughcoating and coloring processes of blue colored cholesteric liquidcrystal (CLC). When a coloring process for a sub-pixel region “Psub” isperformed, a color blurring is generated at a peripheral portion of eachCCF 184 a, 184 b and 184 c. Since a coloring process is performed forall of red, green and blue colors, a color blurring occurs at aperipheral portion of each of the red, green and blue CCFs 184 a, 184 band 184 c. Accordingly, a color blurring region “A” has equal areathroughout the entire substrate 180. Thus, a total area of the colorblurring regions “A” of FIG. 4C is larger than that of FIG. 4B.

For example, a width of the second color blurring region “A2” of FIG. 4Band the color blurring region “A” of FIG. 4C is about 24 μm. In thecolor blurring region “A1,” “A2” and “A,” a helical pitch continuouslyvaries with a value different from that in the sub-pixel region “Psub.”Accordingly, a color blurring region degrades color property of an LCDdevice using a CCF layer. Moreover, a black matrix for shielding a colorblurring region reduces aperture ratio.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a transmissive liquidcrystal display device that substantially obviates one or more of theproblems due to limitations and disadvantages of the related art.

An advantage of the present invention is to provide a liquid crystaldisplay device using a cholesteric liquid crystal color filter layerwhere color property is improved by minimizing a color blurring region.

An advantage of the present invention is to provide a fabricating methodof a liquid crystal display device using a mask, which has an openportion smaller than a sub-pixel region, for a cholesteric liquidcrystal color filter layer.

An advantage of the present invention is to provide transmissive andreflective liquid crystal display devices using a cholesteric liquidcrystal color filter layer where a color blurring region is minimized.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, afabricating method of a substrate for a liquid crystal display deviceincludes: coating a cholesteric liquid crystal material on a substrateto form a cholesteric liquid crystal layer, the substrate having aplurality of sub-pixel regions; disposing a mask having a plurality ofopen portions over the cholesteric liquid crystal layer; irradiating thecholesteric liquid crystal layer through the mask and curing thecholesteric liquid crystal layer, wherein each open portion is smallerthan each sub-pixel region.

In another aspect of the present invention, a fabricating method of asubstrate for a liquid crystal display device includes: coating a firstcholesteric liquid crystal material on a substrate to form a firstcholesteric liquid crystal layer, the substrate having a plurality ofsub-pixel regions; disposing a first mask having a plurality of firstopen portions over the first cholesteric liquid crystal layer;irradiating the first cholesteric liquid crystal layer through the firstmask and curing the first cholesteric liquid crystal layer to form afirst cholesteric liquid crystal color filter layer; coating a secondcholesteric liquid crystal material on the first cholesteric liquidcrystal color filter layer to form a second cholesteric liquid crystallayer; disposing a second mask having a plurality of second openportions over the second cholesteric liquid crystal layer; irradiatingthe second cholesteric liquid crystal layer through the second mask andcuring the second cholesteric liquid crystal layer to form a secondcholesteric liquid crystal color filter layer, wherein each of the firstand second open portions is smaller than each sub-pixel region.

In another aspect, a fabricating method of a liquid crystal displaydevice includes: forming a light absorption layer on a first substratehaving a plurality of sub-pixel regions; coating a cholesteric liquidcrystal material on the light absorption layer to form a cholestericliquid crystal layer; disposing a mask having a plurality of openportions over the cholesteric liquid crystal layer; irradiating thecholesteric liquid crystal layer through the mask and curing thecholesteric liquid crystal layer to form a cholesteric liquid crystalcolor filter layer; forming a common electrode on the cholesteric liquidcrystal color filter layer; forming a gate line on a second substrate;forming a data line crossing the gate line; forming a switching deviceconnected to the gate line and data line; forming a black matrix on thedata line; forming a passivation layer on the black matrix; forming apixel electrode on the passivation layer; attaching the first and secondsubstrates such that the common electrode faces the pixel electrode; andforming a liquid crystal layer between the common electrode and thepixel electrode, wherein each open portion is smaller than eachsub-pixel region.

In another aspect, a fabricating method of a liquid crystal displaydevice includes: coating a first cholesteric liquid crystal material ona substrate to form a first cholesteric liquid crystal layer, thesubstrate having a plurality of sub-pixel regions; disposing a firstmask having a plurality of first open portions over the firstcholesteric liquid crystal layer; irradiating the first cholestericliquid crystal layer through the first mask and curing the firstcholesteric liquid crystal layer to form a first cholesteric liquidcrystal color filter layer; coating a second cholesteric liquid crystalmaterial on the first cholesteric liquid crystal color filter layer toform a second cholesteric liquid crystal layer; disposing a second maskhaving a plurality of second open portions over the second cholestericliquid crystal layer; irradiating the second cholesteric liquid crystallayer through the second mask and curing the second cholesteric liquidcrystal layer to form a second cholesteric liquid crystal color filterlayer; forming a common electrode on the second cholesteric liquidcrystal color filter layer; forming a gate line on a second substrate;forming a data line crossing the gate line; forming a switching deviceconnected to the gate line and data line; forming a black matrix on thedata line; forming a passivation layer on the black matrix; forming apixel electrode on the passivation layer; attaching the first and secondsubstrates such that the common electrode faces the pixel electrode; andforming a liquid crystal layer between the common electrode and thepixel electrode, wherein each of the first and second open portions issmaller than each sub-pixel region.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic plan view of a liquid crystal display deviceaccording to the related art;

FIG. 2 is a schematic cross-sectional view, which is taken along a line“II—II” of FIG. 1, illustrating a liquid crystal display deviceaccording to the related art;

FIG. 3 is a schematic cross-sectional view, taken along a line “II—II”of FIG. 1, showing a liquid crystal display device using a cholestericliquid crystal color filter layer according to the related art;

FIG. 4A is a schematic cross-sectional view of a substrate having anabsorption type color filter layer according to the related art;

FIG. 4B is a schematic cross-sectional view of a substrate having acholesteric liquid crystal color filter layer fabricated through acoloring method excluding a blue coloring process according to therelated art;

FIG. 4C is a schematic cross-sectional view of a substrate having acholesteric liquid color filter layer fabricated through a coloringmethod including a blue coloring process according to the related art;

FIG. 5 is a schematic plane view illustrating a reflective liquidcrystal display device according to a first embodiment of the presentinvention;

FIG. 6 is a schematic cross-sectional view, which is taken along a line“VI—VI” of FIG. 5, showing a reflective liquid crystal display deviceaccording to a first embodiment of the present invention;

FIG. 7 is a schematic plan view showing a mask for a cholesteric liquidcrystal color filter layer of a reflective liquid crystal display deviceaccording to a first embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view showing a relationshipbetween an open portion of a mask and a color blurring;

FIG. 9 is a schematic cross-sectional view illustrating a color filtersubstrate for a reflective liquid crystal display device according to afirst embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view illustrating a transmissiveliquid crystal display device according to a second embodiment of thepresent invention;

FIG. 11 is a schematic block diagram illustrating a fabricating processof red, green and blue cholesteric liquid crystal color filtersaccording to a third embodiment of the present invention;

FIG. 12 is a schematic block diagram illustrating a fabricating processof red, green and blue cholesteric liquid crystal color filtersaccording to a fourth embodiment of the present invention; and

FIG. 13 is a schematic block diagram illustrating a fabricating processof a color filter substrate for a liquid crystal display deviceaccording to a first or second embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, similar reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 5 is a schematic plane view illustrating a reflective liquidcrystal display device according to a first embodiment of the presentinvention.

In FIG. 5, a gate line 254 is formed along a first direction, and a dataline 264 is formed along a second direction crossing the firstdirection. A sub-pixel region “P_(sub)” is defined by a cross of thegate line 254 and the data line 264. A switching device such as a thinfilm transistor (TFT) “T” is formed near the cross of the gate line 254and the data line 264, and a pixel electrode 270 connected to the TFT“T” is formed in each sub-pixel region “P_(sub).” The TFT “T” includes agate electrode 252, and source and drain electrodes 260 and 262. Thegate electrode 252 is connected to the gate line 254 and the sourceelectrode 260 is connected to the data line 264. The source and drainelectrodes 260 and 262 are spaced apart from each other. Even though notshown in FIG. 5, a semiconductor layer is formed between the gateelectrode 252, and the source and drain electrodes 260 and 262. Aportion of the semiconductor layer exposed between the source and drainelectrodes 260 and 262 is a channel region of the TFT “T.” A blackmatrix 266 having an open portion 268 covers a border between theadjacent sub-pixel regions “P_(sub)” and the TFT “T.” Thus, thesub-pixel region “P_(sub)” is exposed through the open portion 268. Red,green and blue cholesteric liquid crystal color filters (CCFs) 214 a,214 b and 214 c corresponding to the open portion 268 are alternatelyformed in the sub-pixel regions “P_(sub).”

FIG. 6 is a schematic cross-sectional view, which is taken along a line“VI—VI” of FIG. 5, illustrating a reflective liquid crystal displaydevice according to a first embodiment of the present invention.

In FIG. 6, first and second substrates 210 and 250 face and are spacedapart from each other. The first and second substrates 210 and 250include a plurality of sub-pixel regions “P_(sub).” A light absorptionlayer 212 is formed on an inner surface of the first substrate 210 and acholesteric liquid crystal color filter (CCF) layer 214 is formed on thelight absorption layer 212. The CCF layer 214 includes red, green andblue CCFs 214 a, 214 b and 214 c in each sub-pixel region “P_(sub).” Acommon electrode 216 is formed on the CCF layer 214.

A gate line (not shown) is formed on an inner surface of the secondsubstrate 250 and a gate insulating layer 256 is formed on the gateline. A data line 264 is formed on the gate insulating layer 256 at aborder between the adjacent sub-pixel regions “P_(sub).” A black matrix265 is formed on the data line 264, and a passivation layer 268 isformed on the black matrix 265. A pixel electrode 270 is formed on thepassivation layer 268 in each sub-pixel region “P_(sub).” Even thoughnot shown in FIG. 6, a switching element such as a thin film transistor(TFT) including a gate electrode, and source and drain electrodes isformed between the second substrate 250 and the passivation layer 268.Moreover, the passivation layer 268 includes a drain contact holeexposing the drain electrode, and the pixel electrode 270 is connectedto the drain electrode of the TFT through the drain contact hole. Aretardation layer 272 and a polarizing layer 274 may be formed on anouter surface of the second substrate 250.

The common electrode 216 and the pixel electrode 270 may be formed of atransparent conductive material such as indium-tin-oxide (ITO) orindium-zinc-oxide (IZO). A liquid crystal layer 280 is formed betweenthe common electrode 216 and the pixel electrode 270. Even though notshown in FIG. 6, first and second alignment layers may be formed on thecommon electrode 216 and the pixel electrode 270, respectively. The CCFlayer 214 may be formed of photochromic cholesteric liquid crystal(CLC). A color blurring region “D” at a border between the adjacent CCFs214 a, 214 b and 214 c is smaller than the color blurring region “A” ofthe related art in FIG. 3. The color blurring region can be reduced byusing an improved mask for the CCF layer 214.

FIG. 7 is a schematic plan view illustrating a mask for a cholestericliquid crystal color filter layer of a reflective liquid crystal displaydevice according to a first embodiment of the present invention.

As discussed previously, a pixel region includes the plurality ofsub-pixel regions “P_(sub)”. Within a single pixel region there may bethree sub-pixel regions: a red sub-pixel region “R”, a green sub-pixelregion “G”, and a blue sub-pixel region “B”. A mask for producing acholesteric liquid crystal color filter according to the presentinvention is illustrated in FIG. 7 overlying a plurality of red, greenand blue sub-pixel regions. As illustrated in FIG. 7, the mask 300 for acholesteric liquid crystal color filter (CCF) layer includes a pluralityof open portions 302. The open portions 302 corresponds to a sub-pixelregion “P_(sub)” having cholesteric liquid crystal to be aligned tocorrespond to the color to be reflected by the CCF. As illustrated, theopen portions 302 may be substantially rectangular, but may be of anyshape suitable for the corresponding sub-pixel region “P_(sub)”. Theopen portions 302 may correspond to the sub-pixel regions to be alignedto reflect a first color, for example, one of red, green or blue. Theremaining sub-pixels are covered by blocking portions of the mask 302.Thus, the number of the open portions 302 may be the same as the numberof sub-pixel regions to be aligned for the first color during asimultaneous exposing process. The cholesteric color filter forsub-pixel regions corresponding to the open portions is formed throughexposing to UV light through the open portions 302. The cholestericliquid crystal is then cured or may be cured after all of thesub-pixels, including those that reflect other colors, have beenexposed. Then, the mask 300 is shifted such that the plurality of openportions 302 correspond to the sub-pixel regions to be aligned toreflect a second color, which may be different than the first color.Then, the sub-pixel regions corresponding to the second color are formedthrough the exposing to UV light. Similarly, sub-pixel regionscorresponding to a third color may be formed by shifting the mask andexposing to UV light. The cholesteric liquid crystal color filtersaligned by the separate exposing processes may be cured after eachrespective exposing processes, or may all be cured together after all ofthe exposing steps have been completed. A CCF layer including the red,green and blue CCFs can thus be completed.

In detail, a cholesteric liquid crystal (CLC) material is coated on asubstrate and an open portion 302 of a mask 300 is disposed over thecoated CLC material to be aligned for a first sub-pixel region“P_(sub).” The coated CLC material is irradiated through the openportion 302 of the mask 300 with a first energy to align the CLC for afirst color. The first color may be, for example, red, green or blue.The irradiated CLC material is cured to form CCFs corresponding to thefirst energy, and thus, the first color. After forming the first CCF,the mask 300 is shifted and aligned to expose a second sub-pixel region“P_(sub)” through the open portion. The coated CLC material isirradiated through the mask 300 with a second energy for a second color.CCFs corresponding to the second color are obtained by curing processthe irradiated CLC material. CCFs corresponding to a third color may beobtained through again shifting the mask and irradiating a third energyonto the CLC material. A CCF layer may thus be completed.

In one aspect of the present invention, the open portion 302 has asmaller area than the sub-pixel region “P_(sub)” to minimize a colorblurring at a border region between the adjacent sub-pixel regions“P_(sub).” For example, when the sub-pixel region “P_(sub)” has a widthof about 90 μm and the black matrix has a width of about 24 μm, the openportion may have a width of about 66 μm.

FIG. 8 is a schematic cross-sectional view illustrating a relationshipbetween an open portion of a mask and a color blurring.

In FIG. 8, a mask 320 is disposed over a cholesteric liquid crystal(CLC) material 314 such that an open portion 322 corresponds to asub-pixel region “P_(sub).” The open portion 322 is smaller than thesub-pixel region “P_(sub).” During a coloring process includingirradiating and curing steps, light passing through the open portion 322is diffused outward at a boundary of the open portion 322 due to opticalphenomenon such as diffraction and interference. The diffused light isirradiated onto the CLC material 314 at a border region of the sub-pixelregion “P_(sub)” and the CLC material 314 at the border region of thesub-pixel region “P_(sub)” has an undesired helical pitch. Accordingly,a color blurring occurs. When the open portion 321 has an area equal tothe sub-pixel region “P_(sub),” as in related art, a first border region321 a for one color does not overlap a second border region 321 b forthe other color. Accordingly, the resulting color blurring region “A” isdoubled. However, when the open portion 322 has a smaller area than thesub-pixel region “P_(sub),” first and second border regions 322 a and322 b overlap each other. Accordingly, the resulting color blurringregion “D” of the present invention is smaller than the resulting colorblurring region “A” of the related art.

FIG. 9 is a schematic cross-sectional view illustrating a color filtersubstrate for a reflective liquid crystal display device according to afirst embodiment of the present invention.

In FIG. 9, a light absorption layer 332 is formed on a substrate 330 anda cholesteric liquid crystal color filter (CCF) layer 334 is formed onthe light absorption layer 332. The CCF layer 334 includes red, greenand blue CCFs 334 a, 334 b and 334 c in sub-pixel region “P_(sub).” Acommon electrode 336 is formed on the CCF layer 334. A color blurringoccurs in the CCF layer 334 at a color blurring region “D” between theadjacent sub-pixel regions “P_(sub).” The color blurring region “D”formed by a mask having an open portion smaller than the sub-pixelregion “P_(sub)” has an area of about a half of a color blurring region“A” formed by a mask having an open portion substantially equal to thesub-pixel region “P_(sub).” Color blurring region “A” is shown in FIG. 9for reference.

FIG. 10 is a schematic cross-sectional view showing a transmissiveliquid crystal display device according to a second embodiment of thepresent invention.

In FIG. 10, first and second substrates 410 and 450 face and are spacedapart from each other. The first and second substrates 410 and 450include a plurality of sub-pixel regions “P_(sub).” A cholesteric liquidcrystal color filter (CCF) layer 414 is formed on an inner surface ofthe first substrate 410, and a common electrode 416 is formed on the CCFlayer 414. The CCF layer 414 includes first and second CCF layers 414 aand 414 b. Light having different wavelength selectively reflects fromthe first and second CCF layers 414 a and 414 b. For example, red CCFmay include a first CCF reflecting green colored light and a second CCFreflecting blue colored light. Accordingly, green colored light and bluecolored light reflect from the first and second CCFs to the backlightunit 490, respectively, and red colored light passes through the redCCF.

A gate line (not shown) is formed on an inner surface of the secondsubstrate 450, and a gate insulating layer 456 is formed on the gateline. A data line 464 is formed on the gate insulating layer 456 at aborder between the adjacent sub-pixel regions “P_(sub).” A black matrix465 is formed on the data line 464, and a passivation layer 468 isformed on the black matrix 465. A pixel electrode 470 is formed on thepassivation layer 468 in each sub-pixel region “P_(sub).” Even thoughnot shown in FIG. 10, a switching element such as a thin film transistor(TFT) including a gate electrode, and source and drain electrodes isformed between the second substrate 450 and the passivation layer 468.Moreover, the passivation layer 468 includes a drain contact holeexposing the drain electrode, such that the pixel electrode 470 isconnected to the drain electrode of the TFT through the drain contacthole. A retardation layer 472 and a polarizing layer 474 may be formedon an outer surface of the second substrate 450. A backlight unit 490 isdisposed under the first substrate 410.

The common electrode 416 and the pixel electrode 470 may be formed of atransparent conductive material such as indium-tin-oxide (ITO) orindium-zinc-oxide (IZO). A liquid crystal layer 480 is formed betweenthe common electrode 416 and the pixel electrode 470. Even though notshown in FIG. 10, first and second alignment layers may be formed on thecommon electrode 416 and the pixel electrode 470, respectively. Thefirst and second CCF layers 414 a and 414 b may be formed ofphotochromic cholesteric liquid crystal (CLC). A color blurring region“D” in the first and second CCF layers 414 a and 414 b at a borderbetween the adjacent sub-pixel regions is smaller than the colorblurring region “A” of the related art as shown in FIG. 3. The colorblurring region can be reduced by using a mask having an open portionsmaller than the sub-pixel region “P_(sub).”

FIG. 11 is a schematic block diagram showing a fabricating process ofred, green and blue cholesteric liquid crystal color filters accordingto a third embodiment of the present invention.

At step ST10, after a photochromic-cholesteric liquid crystal (CLC)material is coated on a substrate having red, green and blue sub-pixelregions to form a CLC layer, a mask having an open portion smaller thanthe sub-pixel region is disposed over the CLC layer such that the openportion corresponds to the red sub-pixel region. The CLC layer isirradiated through the mask with a first irradiation energy to form ared cholesteric liquid crystal color filter (CCF).

At step ST20, the mask is shifted and disposed over the CLC layer suchthat the open portion corresponds to the green sub-pixel region. Then,the CLC layer is irradiated through the mask with a second irradiationenergy to form a green cholesteric liquid crystal color filter (CCF).

At step ST 30, the mask is shifted and disposed over the CLC layer suchthat the open portion corresponds to the blue sub-pixel region. Then,the CLC layer is irradiated through the mask with a third irradiationenergy to form a blue cholesteric liquid crystal color filter (CCF).

In the fabricating process of red, green and blue CCFs, the firstirradiation energy is higher than the second irradiation energy and thesecond irradiation energy is higher than the third irradiation energy.The irradiation energy for red CCF is highest. For example, when thefirst irradiation energy is about 300 mJ, the second and thirdirradiation energies may be about 200 mJ and about 100 mJ, respectively.Even though the red CCF is first formed in FIG. 11, the green or blueCCF may be formed first in another embodiment.

FIG. 12 is a schematic block diagram showing a fabricating process ofred, green and blue cholesteric liquid crystal color filters accordingto a fourth embodiment of the present invention.

At step ST1, a photochromic cholesteric liquid crystal (CLC) material iscoated on a substrate having red, green and blue sub-pixel regions toform a CLC layer.

At step ST2, a mask having first to third open portions is disposed overthe CLC layer such that the first to third open portions correspond tothe red, green and blue sub-pixel regions, respectively. Each of thefirst to third open portions is smaller than each of their respectivered, green and blue sub-pixel regions. The first to third open portionshave first to third transmittances, respectively. The firsttransmittance is higher than the second transmittance and the secondtransmittance is higher than the third transmittance.

At step ST3, the CLC layer is irradiated through the mask. Since thefirst to third open portions have different transmittances, theirradiation energies through the first to third open portions aredifferent from each other. Accordingly, the CLC layer in the redsub-pixel region is irradiated with highest irradiation energy to be ared CCF and the CLC layer in the blue sub-pixel region is irradiatedwith lowest irradiation energy to be a blue CCF. When the CLC materialhaving a helical pitch corresponding to blue color is coated, the thirdopen portion is not necessary. The different transmittances can beobtained by a half tone mask or a slit patterned mask.

FIG. 13 is a schematic block diagram showing a fabricating process of acolor filter substrate for a liquid crystal display device according toa first or second embodiment of the present invention.

At step ST11, a photochromic cholesteric liquid crystal (CLC) materialis coated on a substrate having a sub-pixel region to form a CLC layer.

At step ST22, a mask having an open portion is disposed over the CLClayer and the CLC layer is irradiated through the mask. The open portionis smaller than the sub-pixel region to minimize a color blurring.

At step ST33, the irradiated CLC layer is cured to form a redcholesteric liquid crystal color filter (CCF). Similarly, theirradiating and curing processes may be performed for the green and bluesub-pixel regions by shifting the mask. For a reflective LCD device, alight absorption layer is formed between the substrate and the CLClayer. For a transmissive LCD device, individual coloring processes areperformed for first and second CCF layers.

Since a color blurring at a border region between the adjacent sub-pixelregions is minimized in an LCD device and a fabricating method thereof,a color property can be improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A fabricating method of a substrate for a liquid crystal displaydevice, comprising: coating a first cholesteric liquid crystal materialon a substrate to form a first cholesteric liquid crystal layer, thesubstrate having a plurality of sub-pixel regions; disposing a firstmask having a plurality of first open portions over the firstcholesteric liquid crystal layer; irradiating the first cholestericliquid crystal layer through the open portions of the first mask; curingthe first cholesteric liquid crystal layer to form a first cholestericliquid crystal color filter layer; coating a second cholesteric liquidcrystal material on the first cholesteric liquid crystal color filterlayer to form a second cholesteric liquid crystal layer; disposing asecond mask having a plurality of second open portions over the secondcholesteric liquid crystal layer; irradiating the second cholestericliquid crystal layer through the open portions of the second mask; andcuring the second cholesteric liquid crystal layer to form a secondcholesteric liquid crystal color filter layer, wherein each of the firstand second open portions is smaller than each sub-pixel region.
 2. Themethod according to claim 1, wherein the first mask and the second maskare the same mask.
 3. The method according to claim 1, wherein theplurality of sub-pixel regions include red sub-pixel regions, greensub-pixel regions and blue sub-pixel regions.
 4. The method according toclaim 3, wherein the first and second cholesteric liquid crystal colorfilter layers in the red sub-pixel regions reflect green and bluecolored lights, respectively, wherein the first and second cholestericliquid crystal color filter layers in the green sub-pixel regionsreflect blue and red colored lights, respectively, wherein the first andsecond cholesteric liquid crystal color filter layers in the bluesub-pixel regions reflect red and green colored lights, respectively. 5.A fabricating method of a liquid crystal display device, comprising:coating a first cholesteric liquid crystal material on a substrate toform a first cholesteric liquid crystal layer, the substrate having aplurality of sub-pixel regions; disposing a first mask having aplurality of first open portions over the first cholesteric liquidcrystal layer; irradiating the first cholesteric liquid crystal layerthrough the open portions the first mask; curing the first cholestericliquid crystal layer to form a first cholesteric liquid crystal colorfilter layer; coating a second cholesteric liquid crystal material onthe first cholesteric liquid crystal color filter layer to form a secondcholesteric liquid crystal layer; disposing a second mask having aplurality of second open portions over the second cholesteric liquidcrystal layer; irradiating the second cholesteric liquid crystal layerthrough the open portions of the second mask; curing the secondcholesteric liquid crystal layer to form a second cholesteric liquidcrystal color filter layer; forming a common electrode on the secondcholesteric liquid crystal color filter layer; forming a gate line on asecond substrate; forming a data line crossing the gate line; forming aswitching device connected to the gate line and data line; forming apassivation layer on the switching device; forming a pixel electrode onthe passivation layer; attaching the first and second substrates suchthat the common electrode faces the pixel electrode; and forming aliquid crystal layer between the common electrode and the pixelelectrode, wherein each of the first and second open portions is smallerthan each sub-pixel region.
 6. The method of claim 5, wherein the firstmask and the second mask are the same mask.
 7. The method of claim 5,further comprising forming a black matrix on the data line.